code: def fnirs_epochs():
      """Create an fnirs epoch structure."""
      raw_intensity = read_raw_nirx(fname_nirx, preload=False)
      raw_od = optical_density(raw_intensity)
      raw_haemo = beer_lambert_law(raw_od, ppf=6.0)
      evts, _ = events_from_annotations(raw_haemo, event_id={"1.0": 1})
      evts_dct = {"A": 1}
      tn, tx = -1, 2
      epochs = Epochs(
          raw_haemo, evts, event_id=evts_dct, tmin=tn, tmax=tx
      )
      return epochs
  
file_path: mne-python/mne/viz/conftest.py
imports: import os.path
  import numpy
  import pytest
  from mne import Epochs, EvokedArray, create_info, events_from_annotations
  from mne.channels import make_standard_montage
  from mne.datasets.testing import _pytest_param, data_path
  from mne.io import read_raw_nirx
  from mne.preprocessing.nirs import beer_lambert_law, optical_density
label_desc: Use image node_id 2 for calling a global function with example usage: fnirs_epochs() and returns: epochs